Gas-turbine engine with failure-operated control means



March 29, 1960 HAWQRTH ET AL 2,930,188 GAS-TURBINE ENGINE WITH FAILURE-OPERATED CONTROL MEANS Filed Oct. 50, 1957 United States Patent GAS-TURBINE ENGINE WITH FAILURE- OPERATED CONTROL lVlEANS Lionel Haworth, Loughborongh, and Donald McLean,

Derby, England; said Haworth assignor to Rolls- Royce Limited, Derby, England, a British company Application October 30, 1957, Serial No. 693,297

Claims priority, application Great Britain November 8, 1956 Claims. (Cl. 6039.09)

This invention relates to gas-turbine engines of the kind which comprises a turbine rotor and a coaxial driven member such as a compressor rotor, or the reduction gear of a propeller, which are interconnected by 'a driving shaft. Such gas-turbine engines will be referred to as being of the class specified.

It will be appreciated that, in the event of'failure of the driving shaft, the turbine rotor will accelerate rapidly due to the removal of the load it is driving and that unless such acceleration is prevented over-speeding and serious damage, such as bursting of the turbine rotor, may occur.

This invention has for an object to provide control means which responds rapidly to shaft failure to prevent such overspeeding.

In accordance with the present invention is a gas turbine engine of the class specified, a tube or theequivalent is provided which extends within the'd'riving shaft and is drivingly connected to the shaft atspaced locati'o'ns, one such location being in the region of the load, e.g. the compressor rotor, and another such location being in the region of the turbine rotor, said tube or equivalent being fed with a fluid under pressure thereby to provide a pressurised chamber, which chamber is connected to pressure-responsive means controlling the supply of fuel to the engine, the arrangement being such that in the event of fracture of the shaft said tube or the equivalent is also fractured, resulting in reduction of pressure on the pressure-sensitive means thereby to reduce the fuel supply to the engine.

According to a preferred arrangement of the present invention, a gas-turbine engine of the class specified has a rotor system which includes a hollow driving shaft and a tube extending through the shaft, the tube being drivingly connected to the rotor system adjacent the turbine and adjacent the load and the wall of the tube being weakened at a' location between said driving connections so that the tube fractures at said location on failure of the shaft, and the tube having within it means defining with the weakened portion of the wall a chamber of limited volume having a restricted inlet, and comprises means to supply pressure fluid to the chamber through said inlet, and means responsive to the pressure within the chamber and operative on fall of pressure within the chamber to cut down the fuel supply to the engine.

In use, on fracture of the tube, there will be a rapid loss of pressure fluid from the chamber and the consequent fall of pressure is employed as a signal for rapidly reducing the fuel supply. In order to ensure the most rapid response, it is preferred to deliver a liquid under pressure to the tube.

According to an important feature of arrangements employing a pressure liquid, means is connected to the chamber to permit any air (or other gas) separating from the pressure liquid to be led away from the chamber.

Any air under pressure in the chamber will reduce the rate of response of the control and thus it is desirable that the chamber be bled of free air (or other gas).

2,930,188 Patented Ma r. 2 9,

In one practical embodiment of the invention, the tube is fed with lubricating oil under pressure and the tube is also employed as an oil distributor for the bearings of the rotor system.

One embodiment of this invention will now be described with reference to the accompanying drawings, in which- Figure 1 illustrates diagrammatically a simple gas turbine engine and shows parts of the engine lubricating and fuel systems and a failure control arrangement. of this invention, and

Figure 2 shows in greater detail a construction bodying features illustrated in Figure 1.

Referring first to Figure l, the engine comprises an axial-flow compressor having a statorcasing 10a and a rotor 10b, combustion equipment 11 which receives air compressed in the compressor and has fuel fed to it through injector nozzles 12, and a turbine havinga casing 13a and rotor 13b, which turbine receives the com; bustion products from the combustion equipment 11. The turbine rotor 13b is drivingly connected to the compressor rotor 10b by a hollow driving shaft 14.

The fuel system is of any known or convenient kind and that illustrated comprises a multi-piston swash-plate pump 15 which is engine driven and which is controlled as to its delivery by a servo motor under control of a unit 16. The pump draws in fuel through suction pipe" -17 and delivers through pipe 18 past a throttle 19 to a manifold 20 from which branches lead to the injector nozzles 12. I

The servo motor controlling the pump 15 comprises a piston 21 separating two pressure spaces 22, 23, where? of the space 22 is directly connected through a duct 24 with the delivery pipe 18 of the pump and of which the" space 23 is connected to the delivery of the pump through a restricted orifice 25. A spring 26 is accommodated within the space 23 and urges the piston 21 to a position corresponding to maximum fuel delivery of the pump. The pressure space 23 also has connected to it a bleed pipe 27, the opposite end of which is controlled by a half ball valve element 28 forming part of the control unit 16. It will be clear that when the valve element 28 lifts a greater flow occurs through the bleed her. The lever 30 carries the valve element 28 at one:

end and also has bearing on this end a spring 31'and'a push rod 32 which is loaded hydraulically by ,a piston.

element 3-3 subjected on one side to thefueldelivery; pressure through conduit '34, The spring 31 tends to close the valve 28 on to the end of the bleed pipe 27 and the fuel delivery pressure acting through the push rod 32 tends to lift the valve element off the end of the. bleed pipe 27. It will thus be seen that an increase in;

the fuel delivery pressure tends to cause a decrease in the fuel delivery of the pump 15 and that a'fall'in the fuel delivery pressure tends to cause an increase in the.

fuel delivery pressure.

The opposite end of the lever 30 is loaded in the sense to lift the valve element 28 off the'end of the pipe-27 by an evacuated capsule 35 and the chamber nouns-gor the capsule is open to atmosphere through port 36. It

pipe '27; and the pressure within the space 23 will fall so that} the servo piston 21 will move to the right as seen in the will be clear that as the atmospheric prmsure increases so the capsule 35 will collapse reducing the load applied by the capsule on the lever and thus tending to increase the fuel delivery, and conversely, if the atmospheric pressure falls, say due to increase of altitude on operation of the engine, the load applied by the capsule 35 on the lever 30 increases lifting the valve element 28 and causing a decrease in the fuel delivery of the pump 15.

The lubricating system of the engine comprises a lubricating oil pump 37 delivering oil through a pipe 38 to a muff 39 from which the pressure oil is fed into a tube 40 rotating with the rotor system of the engine. The oil may be fed from the tube to the bearings of the rotor system in any convenient manner.

It will be understood that should the shaft 14 connecting the turbine rotor 13b to the compressor rotor b fail in operation there will be a tendency for the turbine rotor to overspeed if the fuel supply to the engine is not cut down rapidly and a control is provided whereby the danger of overspeeding in these circumstances can be avoided.

For this purpose the tube 40 is drivingly connected with the rotor system by two sets of splines, of which splines 41 drivingly connect one end of the tube to the compressor rotor 10b and the other set of splines 42 drivingly connect the opposite end of the tube to the turbine rotor 13!), preferably to a stub shaft 43 projecting downstream from the turbine disc into a central bullet 44 of the turbine exhaust assembly.

A constriction 45 is formed intern-ally of the tube at a position remote from the oil supply muff 39 so as to define with the wall of the tube a chamber 46' of limited capacity having a restricted oil inlet. The portion of the tube wall defining the chamber 46' is provided with a shear neck in the form of -a helical groove 47 and thus it will be clear that in the event of failure of the dri-ving shaft 14 the tube 40 will be quickly fractured in the region of the shear neck 47.

The chamber 46 is placed in communication with pressure-responsive means through ducting 48 ard there is also provided a deaerator 49 so that any air separating from the lubricating oil within the chamber is bled off from the chamber.

The pressure-responsive means comprises a casing 50 divided into three chambers 53, 54, 58 by a flexible diaphragm 51 and a rigid wall 52. The conduit 48 opens into the chamber 53 so that the diaphragm 51 is subjected on one side to the pressure within the chamber 46 and the chamber 54 on the opposite side of the diaphragm 51 is open to atmosphere through polts 55. A spring 56 is accommodated within the chamber 54 and loads the diaphragm 51 in opposition to the fluid pressure in chamber 53.

The diaphragm has secured centrally to it a stem 57 which passes through the wall 52 into the third chamber 58 and the stem 57 carries at its lower end a half ball valve element 59 co-operating with the end of a branch 60 from the bleed pipe 27. A drain pipe 61 leads from the chamber 58, for example back to the suction side of the pump 15.

It will be clear that in normal operation the pressure of the lubricating oil within the chamber 46 acting on the diaphragm 51 holds the half ball valve element 59 on the end of the branch bleed pipe 60, but that in the event of fracture of the tube 40 at the shear neck 47, the pressure within the chamber 46 (and thus the pressure acting on the diaphragm 51) will fall rapidly and the spring 56 will urge the diaphragm 51 upwardly so lifting the valve element 59 off the end of branch bleed pipe 60 and permitting a bleed flow from space 23 thereby to cause the delivery of the pump rapidly to be reduced.

A manually-controlled lever 50a is provided on the casing 50 to permit the half-ball valve 59 to be held closed while oil pressure is building up in the chamber 53 during starting.

Referring to Figure 2, it will be seen that the end of the tube 40 projects beyond the stub shaft 43 towards stationary structure 62. The stationary structure has a closed space 64 defined within it by means of a cup member 63 and the cup member supports a flanged plug 65 the stem of which projects into and seals the bore of the tube 40. The plug 65 has a central bore 66 leading from within the chamber 46 to the closed space 64 into which also opens one end of the ducting 48.

From the upper wall of the space 64 an air bleed duct 67 leads to a cavity 68 in the stationary structure and the cavity contains a sleeve 69 engaged by a landed plug 70 providing a restricted passage for air separating from the lubricant in operation.

The plug 65 is retained axially in position in the cup member 63 by a flange 65a on the plug being sandwiched between an internal flange 63a of the cup member and a plate 71 retained by a spring circular retaining clip 71a. The lubricating oil pressure within the space 64 pressure loads the flange 65a against the flange 63a. However the plug 65 is free to rotate relatively to the stationary structure and to the tube 40.

Although the invention has been described in its ap plication to a simple gas-turbine engine, the invention can also be used with marked advantages in connection with compound gas-turbine engines and especially propeller-driving compound gas-turbine engines. A com.- pound gas-turbine engine comprises a low-pressure compressor, a high-pressure compressor, a high-pressure turbine drivingly connected to the high-pressure compressor and the low-pressure turbine drivingly connected to the low-pressure compressor and also through a reduction gear to the propeller where such is provided. In such engines as used for aircraft propulsion it is common to arrange the low-pressure driving shaft coaxially within the high-pressure driving shaft and in applying the invention to such an engine the tube associated with the failure control may be accommodated within the lowpressure shaft and be drivingly connected to the lowpressure turbine rotor and the low-pressure compressor rotor. In such an arrangement the lubricating oil may be fed from the tube to inter-shaft bearings.

We claim:

1. A gas-turbine engine of the class specified comprising a fuel supply system and a pressure fluid source separate from the fuel system and further comprising a tube or the equivalent which extends within the driving shaft and is drivingly connected to the shaft at spaced locations, one such location being in the region of the load, and another such location being in the region of the turbine rotor, said tube or equivalent being fed with fluid under pressure from said pressure fluid source thereby to provide a pressurised chamber, which chamber is connected to pressure-responsive means controlling the supply of fuel to the engine, the arrangement being such that in the event of fracture of the shaft said tube or the equivalent is also fractured, resulting in reduction of pressure on the pressure-sensitive mean thereby to reduce the fuel supply by the fuel supply means to the engine.

2. A gas-turbine engine of the class specified comprising a fuel supply system, the rotor system including a hollow driving shaft and a tube extending through the shaft, the tube being drivingly connected to the rotor system adjacent the turbine and adjacent the load and the wall of the tube being weakened at a location between said driving connections so that the tube fractures at said location on failure of the shaft, and the tube having within it means defining with the weakened portion of the wall a. chamber of limited volume having a restricted inlet, and comprising also pressure fluid supply means separate from said fuel system and connected to supply pressure fluid to the chamber through said inlet,

3. A gas-turbine engine according to claim 2, wherein Y the turbine has a shaft extension on the side thereof remote from the load, the tube extending in said extension, and the first driving connection between the tube' and the rotor system being through said shaft extension, and the restricted inlet and weakened portion of the tube being adjacent the turbine.

4. A gas-turbine engine according to claim 2 wherein the fiuid is a liquid under pressure.

5. A gas-turbine engine according to claim 4, comprising also means connected to the chamber to permit gas separating from the pressure liquid to be led away from the chamber.

6. A gas-turbine engine according to claim 4, wherein the liquid is lubricating oil under pressure and the tube is also employed as an oil distributor for the bearings of the rotor system.

7. A gas-turbine engine as claimed in claim 2, comprising means effecting the fuel supply to the engine, which means includes a servo-mechanism controlling the fuel delivery to the engine and having a servo-fluid bleed pipe flow through which controls the operation of the servo-mechanism, and wherein the pressure-responsive means actuates a bleed valve at an outlet from the bleed pipe in the sense to decrease the fuel delivery when the pressure to which the pressure-responsive means is subjected falls.

8. A gas-turbine engine according to claim 7, wherein the pressure-responsive means comprises a flexible diaphragm separating a pair of chambers, the bleed valve being carried by the diaphragm, one of the chambers separated by the diaphragm being connected to the chamber within said tube so that the diaphragm is loaded in one sense by the pressure in the chamber in the tube and the diaphragm being loaded in' the opposite sense by a spring contained in the other of the pair of chambers, the said other chamber being connected to atmosphere.

9. A gas turbine engine comprising a rotor system including a turbine rotor, a co-axial driven member, a hollow driving shaft drivingly interconnecting the turbine rotor and the driven member and a hollow shaft extension on the side of the turbine rotor remote from the driven member, a tube extending from adjacent the driven member through a driving shaft and the shaft extension and having an end portion projecting beyond the end of the shaft extension, a first driving connection interconnecting the tube and shaft extension, a second driving connection interconnecting the tube and the rotor system adjacent the driven member, the tube having a weakened wall portion 6 the second driving connection, means to supply pressure fluid to said tube at its end adjacent the second driving connection, stationary structure having a chamber therein, a plug having a bore therein, the plug being rotationally mounted in the stationary structure and engaging the projecting end portion of the tube with freedom for relative rotation thereto, the bore of the plug interconnecting the tube and the chamber, fuel supply means delivering fuel to the engine, and pressure-responsive means connected to said chamber to respond to the pressure therein and operative on fall of pressure within the chamber to cut down the fuel supply to the engine.

10. A gas turbine engine as claimed in claim 9, wherein said means to supply pressure fluid supplies liquid under pressure to the end of the tube adjacent the second driving connection.

11. A gas-turbine engine according to claimlO, comprising also means connected to said chamber to conduct gas separating from the pressure liquid away'from said chamber.

12. A' gas turbine engine according to claim 11, wherein said means to conduct gas away from said chamber comprisesv a restricted outlet from the upper side of the chamber. V

13. A gas turbine engine according to claim 10, comprising bearings supporting said rotor system in said sta tionary structure, said tube being employed as an oil distributor for said bearings and said means supplying pressure liquid to the tube being, adapted to supply lubricating oil to the tube. v 14. A'gas turbine engine as claimed in claim 9, wherein the fuel supply means includes a servomechanism controlling the fuel delivery to the engine and having a servo-fluid bleed pipe flow through which controls the operation of the servo-mechanism, and wherein the pressure-responsive means actuates a bleed valve at an outlet from the bleed pipe in the sense to decrease the fuel delivery when the pressure to which the pressureresponsive means is subjected, falls.

15. A gas turbine engine according to claim 14, wherein the pressure-responsive means comprises a flexible diaphragm separating a pair of chambers, the bleed valve being carried by the diaphragm, one of the chambers separated by the diaphragm being connected to the chamber within said tube so that the diaphragm is loaded in one sense by the pressure in the chamber in the tube and the diaphragm being loaded in the opposite sense by a spring contained in the otherof the pair of chambers,

between the said driving connections and adjacent the turbine whereby on failure of the driving shaft the tube fractures at said weakened wall portion, a flow restriction within the tube between said weakened wall portion and the said other chamber being connected to atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS Gaubatz Nov. 2, 1954 UNITED STATES PATENT OFFICE v CERTIFICATE OF CORRECTION Patent No. 2,930,188 March 29, 1960 Lionel Haworth et al0 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the grant, lines 1, 2, and 3, for "Lionel Haworth, of Loughborough, and Donald McLean, of Derby, England; said Haworth assignor to fiolls Royce Limited, of Derby, England,

a British company," read Lionel Haworth, of Loughborough, and Donald McLean, of Derby, England, assignors to Rolls-Royce Limited, of Derby, England, a British company, lines 12 and 13, for "Donald McLean, his heirs or assigns, and Rolls Royce Limited, its successors" read Rolls-Royce Limited, its successors in the heading to the printed specification, lines 4, 5, and 6, for "Lionel Haworth, Loughborough, and Donald McLean, Derby, England; said Haworth assignor to Rolls- Royce Limited, Derby, England, a British company" read Lionel Haworth, Loughborough, and Donald McLean, Derby, England, assignors to ERolls-Royce Limited, Derby, England,

a British company Signed and sealed this 4th day of October 1960; wf f (SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

